Danger detecting means for gas distributing systems



1952 G. WEISSMAN ETAL 2,535,882

DANGER DETECTING MEANS FOR GAS DISTRIBUTING SYSTEMS Filed 001. 12, 1945 2 SHEETSSHEET 1 sousnom IN V EN TORS 1952 G. L. WEISSMAN ETAL 2,

DANGER DETECTING MEANS FOR I GAS DISTRIBUTING SYSTEMS Filed Oct. 12, 1945 2 SHEETS-SHEET 2 I I vl3 H SOLENOID V J TORS Patented Feb. 12, 1952 DANGER DETECTING-MEANS FOR GAS DISTRIBUTING SYSTEMS George LT Weissman and Howard A.'Gra'fiis;'De-

' man said'Weiss- ApplicatiorvOctober- 12, 1945;.Serial No.- 621,924

6 Claims. 1 I I --'Ihe -invention relatesto apparatus for use in connection with gas distributingsystems and. it.- is' the primary object :of the inventiomto-de- Wt-ect dangeror possible danger-in the operation. PI-t is a furtherobject toiprovide detecting means for the presence of an inflammable mixture-of Wair-Iandl-gas 1 ina selected area,.- also ,for detecting failure tof gasypressurerin the supply. system which mightnsult =in the extinguishing of a gas #burnerwiththe subsequent escape of gas therefrom. -=Still-furtheritis an object to detect any inoperative condition 'in -v the detecting apparatus "which would cause failure inoperation thereof. 1 It is :a further object to utilize the detection means -either for warning of possible danger or i'ior-the'actual cutting-off of the gas supply thereby eliminating the danger.

The above andothen-objects are realized in accordance with thepresent invention .by passing -atcurrentofgas taken frointhe atmosphere of a @selected space which -may besuspected of con- :taining az-dangerous explosive, or near explosive cmixture of gases,-- through a flash-back arrester into and through an ignition chamber enclosed :away' from the selected space, first-passing the current of :gas within saidchamber-into contact with :andqpast a normally functioning source of heat within said chamber whereby the gases of said current are normally broughtto a temperaiture at least; great enough to ignite a any ignitable Vmixture-contained therein and cause it to burn, hand then carrying the resulting current of nor- "many-heated gasesinto contact with and past temperature --responsive means attached to said whamber whereby a source of powerfor a warning =.-device or, preferably, a-source of power for a ,fgasrfiow controlling device operatively'connected to -thewmain supply'line of a combustible. gas,

lisvputninto operation in response to predetery,

.iminedw' changes, increases or decreases, in the atemperature of said normally heatedgases. "The method-isespecially valuable because it not only Y iunctions to positively eliminate danger before an explosive mixture develops-or as soon-as such.

zap-mixture is present but also gives warning or automatically shuts ofi a combustible gas supply whenever the heat source used inthe method fails.

The :novel means andapparatus combinations :idescribed herein are especially suitable for use in 1the-above mentioned 1 new method of warnking or of control of acombustible gassupply.

The invention will be understood by reference tothe accompanying-drawings and the descrip-e ltions .of the same and theirfinctions"-givenbeilow.

Fig'. l of .the' drawings'is a 'funb'tionaldiagram wherein --.the symbols represenv' enerm "'me'ans l -,and .their functions, 'raIther'itliaIfany particular 3 form" of apparatus; thereby clarifying "thecomplete new warning and'fflow co'iitrollingprocess and the interrelationships" of the various s't'e'ps therein; Fig. 2 an"elevation,"showing a'preferred i0 embodiment of apparatus for carryingwut the fiow'cdntrio lling processjfwhich is1arge1 in' "crosssection but having illirfiit ed portions of the figure l around the centrally ldcated"thermoiesponsive partnappearing infull open 'viewfFigl' 3ari'fenlfielargedide'tail in cfdssi-s'eiftibnb'fth'bl nitajllic thermoresponsive element and" 'sii' itcl imembers cooperating therewith". itak'en' altii'ig line" 3 3 "of :Figf ,2 .andiFigI if is wiring" diagram showing the electrical connections "used" with the apparatus ifofTFig'. 2 Tand'is particularly useful be- -caus it' shows 'the internal Wiring of l the'switch box "(if Fig. Z-and' alsose'rvestc illustrate the 'mode =of operation loflthe two normally'closed; single pole, single throw,maintained cofit'act type mi'cro wswitches equipped ,withfi'nanual'fes'et pins which are contained. in ltheswitclibox of Fig; :2. j Jnth functional aiagrampr Fig; lthere are shown a mam: supply lines for combustible, gas, a warning device w'afld/ "01 a; controlling means 3 V forggiving a; warning lsi'gnal 'oractually" con- :trolling .the supply fof said gas; "andfins'erted in lin S if a controllingmeans but either entirely separate iron'i line S or connected "therewith; as Y. desired; if awarning device wni'ea'ns; a chamber -A havingianli'nlet A1"for"the"gas at one end-thereof .andiari outlet A'zspaced a'conveni'ent d'istancfrom. inlet 'Ai to form an' 'ignitionchamberwithin chamber-ATlarge-"enough to accommowlatea flashback LarfestenF a"'heat"'supplying 4O -region" X and a .heat"transferi space"Yfon"the"opsposite. side Iof regiori X" froml'arrester' F,1a heat source Huopposit region X for heating the] same and also.igniting comb ustible' 'gas mi'Xtures"fi0w ing through lchamb'er A; a im'eansRiocat'ed op- 5: :positec-space Y and" responsive to temperature :changes therein so as to actuate a'source'br power and'danger -cletecting'.device P- which is operatively oonnected -to means R and :actuat'es the same to automatically produce "movement or proper f-unctioning of'warning and/ or controlling -;means V corresponding to said -temperature :changes.

v{Ilia-arrows(at inlet Aland-outlet Azindicate di- -3'1?eetiOl1 fi,gaS-fi0W causedby pressureat the rig'ht of-the-arrowsor suction at-theleftand ahead of the arrows, or by combination of the pressure and suction. Means for producing thepressure and/or suction with consequent flow of gas through A may consist of any of the conventional or known means for so operating. However, in the preferred method, the gas flow producing means for chamber A is operative by virtue of normally continuous pressure in line S on the delivery side of a valve V inserted in S which is transmitted to and serves to operate said gas flow producing means. This is indicated by dotted line L of Fig. l, but is more clearly illustrated by the embodiment of the invention as shown in Fig. 2 where a venturi or jet located back of a pilot is connected to the main gas supply line on the delivery side of the main gas supply line valve and is used to produce suction and hence flow of gas through the ignition chamber and past the heated wire filament.

At least a general idea of the operation of the method of the present invention can be understood by reference to Fig. 1. Thus, when there are no leaks in the gas supply system of which the main supply line S is shown, and when there is adequate combustion of gas at delivery points of the system and no gases or flammable vapors from any source whatsoever are being released andd drawn into chamber A, the flow through chamber A consists mainly of ordinary air, with perhaps a small percentage of burned gases in those instances where gas from supply line S is being burned outside of chamber A for normal heating or power purposes. Under such normal circumstances, there is a constant supply of heat by source H and also a constant and continuous transfer of heat from region X to space Y with no appreciable temperature fluctuations in space Y, since the flow of air through A is also substantially constant. Now any one or all of several dangerous circumstances can arise but the method diagrammed in Fig. 1 will promptly and automatically operate to remove the danger of flre and explosion by completely shutting off the supply of gas in line S.

If there is a failure of heat supply means H there will be a decrease in temperature in space Y which will cause temperature responsive means R to actuate device P to shut off the supply at controlling means V.

If a leak occurs in the vicinity of chamber A, the combustible gas and air mixture formed will be forced through chamber A and ignited by the high temperature in heat supplying region X, the additional heat of the resulting combustion causing a temperature increase in space Y which likewise automatically causes temperature responsive means R to actuate device P to shut off the gas supply at controlling means V. Conduits or pipes can be used to conduct gases or flammable vapors from distant points up to chamber A, so that the method operates as a result of the presence of dangerous mixtures of air or like oxidizing gas with combustible gas or flammable vapors at places located remote from chamber A and even when combustible gases or vapors of difierent chemical composition from that in line S are present or when they are derived from sources not connected in any way with the gases in supply line S.

In the preferred method where gases are caused to flow through the ignition chamber by virtue of normally continuous gas pressure on the delivery side of the main supply valve or regulator, such as where a Venturi-backed pilot burner is burning and is connected with line S on the delivery side of controlling means V, as indicated by dotted line L, the method is especially efficient because the pilot burner (a potential means for igniting explosive mixtures) not only goes out when the main gas supply is shut off at controller V, but controller V itself is automatically made to shut off the supply whenever the pilot burner is blown out or otherwise extinguished while controller V is still open or in the on position. This latter action occurs because the unburned gases escaping at the extinguished pilot burner are carried into and burned in chamber A and then drawn past space Y, thereby producing the necessary temperature increase in space Y to cause the main supply to be shut off. This action can be made to occur more quickly and more certainly by having inlet A1 of A near the pilot burner or directly connected by a, pipe to a point very near to the pilot burner.

Actual operation of the method and especially the preferred method, as well as new and novel apparatus useful for carrying out the preferred method, can be even better understood by reference to Fig. 2 with reference to Figs. 3 and 45 where necessary.

Fig. 2 shows a pipe I, which supplies combustible gas, taken from the delivery side of the main gas supply line valve 24, to a jet 3 which supplies gas through pipe 2 to a conventional pilot light, not shown. Flow of the gas through the jet 3 located in T-connection 4 produces suction in the ignition or combustion chamber consisting of fire-resistant nipples 5 and 5 and T- connection 1, thereby sucking gases into said chamber through tubes 8 and 9 fitted into the cap 25 that is fastened onto the outer end of nipple 6 in an airtight manner.

Tube 8 can be of short length because pipe 2 is customarily short for a pilot burner and the flame of the pilot burner at its upper end is therefore fairly near to cap 25. However, it is preferred that the end of tube 8 extend to a point very near to the pilot flame and not more than an inch or two away from the flame, so that the entire apparatus will function quickly in case the pilot flame is accidentally blown out. Only one tube, such as tube 8, carrying atmosphere from the space in the immediate vicinity of the pilot flame is necessary for operation of the method when using the apparatus of Fig. 2. Nevertheless, tube 9 is also shown, since a plurality of tubes leading from different selected spaces other than that near the pilot flame can also be present. For example, tube 9 can lead from a point near a main burner for gas derived from the main supply line. Since the volume of gas flowing through a main burner is ordinarily much greater than that flowing through the pilot, the preferred and safest apparatus is that having tubes passing through cap 25 that not only carry atmosphere from near the pilot flame but from all other points where combustible gas is being delivered which could be ignited by the pilot flame or like source of heat.

It is of course to be understood that instead of having separate tubes leading to the ignition chamber from each selected space intended to influence operation of the shut-01f method during periods of danger, one can provide a minimum of only one tube, such as tube 8, which is branched in any desired manner to bring atmosphere from the vicinity of one or more pilot flames and also at the same time from one or more burners. The single delivery tube, such as 8;-can also have abranch or some of-its branches extending to the open air of rooms orother "spaces not -located close to a regular delivery .point for the combustible gas.

-An airtight-switch-box lis shownin Fig. 2 and is screwed into the T-connection 1 in anairtight .manner. Inside of switch box [0 there are two spring leaf 7 actuated snap action switches,

not shown in Fig. 2 but represented diagram- 'matic'ally inthe wiring diagram of Fig. 4. The "switches have. manual' reset buttons which are :operated in airtight-manner through the walls of switch box I0 by means of front screw 2|, shown in Fig. 2,.and: alike back 'screw, not shown, located on'the other side of switch'box .10 from .screw 2 I. Terminals for the two switches, which are connected electrically in series,- are shown at .19 and 20. Cap 22tis1screwed onto switch box I 0 .after the switches are installed and this :"serves to :makesaid switch boxsubstantially air- .tight.

.fiBilectricEtl heating resistor N connectedto a .sourcesof electricalpowerat points I7 andlt supplies heat which is transmitted at least in part. to bimetallic thermoresponsive element i 2 which is normally kept ata more or less uniform temperaturecausingits free movable end to hold a substantially constant normal position mid: way :between .the tips 14 and i5 of the spring .leaf actuatorsof the twosnap action switches. Bimetallic element I 2; is rigidlyznounted or fixed -inv thestreamlined support 13 attached-to T- connection 1. Although. thermoresponsive element ;l2;is referred to as being f bimetallic, this termis intended to include any equivalent element made up of stripsof.closelyadhering metals .having difieringcoeflicientsof expansion whether two orimorezmetalsor. two. ormore strips are eused.

'HGisatightly wound. coilof Wire gauze wedged "intoxnipple. 6 and serving as. a-flash-back arrester.

;Solenoid 23. is connected electrically" in series (Fall 1941) of. General Controls Co.

In- Fig. 4 there is shown the" wiring diagram arsed with theapparatus of Fig. 2. The current supplied at terminals I! and I8 is 24 volt 60 cycle alternating current which can for example be brought down by a step-down transformer'from the ordinary 110 volt 60 cyclecurrent used for household purposes. Parts H, .12, 14, and 23 'of Fig. 4 represent the heat- ;ing. resistor, bimetallic .thermoresponsive ele- I ment, two spring leaf actuator tips and solenoid respectively of Fig. 2. switches 3lxand 32:.are of the normally closed, single" pole, single throw, maintained-contact The two snap action type micro switches equipped with-plunger pins nah-and All. and manualreset pins 31 and mspectively. A switch of this type is described on :page 1.07: of Micro Precision Snap Action :Switches Catalog NoJ 60' (1941) of the Micro -1 Switch Corporation, Freeport, Illinois,- as well 1 tact points 34. and "36.

vmercial heating or power purposes.

6 f as on other pages .of: this :catalog and: in: United St'atesPatent No..=l,960,020 I F'ig'.c.4uillustrate the normally: closed micro switch-solenoid seriesecircuit in parallel with the electricalxheating: resistor (II circuit. When temperature changes causethe free end of himetallic element i2 to press against tip'ld or 55,. plunger-1 39.01 '40 is depressed and causes snapaactionxbreakage of electrical contact'between contact points *34 and -35 or -between con- Regardless of I which contact is broken, or if both-are broken, the

series circuit is thereby broken and current -,.c.eases to flow through the solenoid. This failure .madexcontact will,: however, immediatelybe -broken unless the thermoresponsive element 12 is kept between tips l4 and I5 and is not exerting -=pressure on eitherjtip. So also when thevalve operator 23 closes valve 24, the latter will stay closed until the operator is manually reset in the open or .on position again.

Cycle of operations A 2 complete .cycle, from the setting of the apparatus into operation, through the final shutoifstage and up to the point where they apparatus .is .again .ready for operation, will now be described with referenceto Fig. 2, 3 and 4.

Assuming that main gas supply linevalve'24 is open-iand maintained in that position in consequence of current flowing continuously through the :solenoid of valve operator 23, the jet 3 and {ya-main burner, not shown but located near the 4 outer open end of tube 9, will then be supplied with combustible gas, such as the artificial or natural gas ordinarily used for household or com- The heating resistor'circuit is always closed and 6 volt,

= cycle electric energy is supplied at terminals H and I8 (e. g. by an ordinary 4 watt bell-ringing transformer) to keep the B. & S. Zia-gauge Chromel-A nickel, zochromium alloy) wire (Nichrome wire) at a temperature of about 600 C. or. higher. #This requires about 0.7 ampere of current: for a. 20 turn coil with inch in diameterturns. and about an 8 inch straight'wire length.

The plunger-of the solenoid of 23 act merely as a keeperof a mechanismthat releases strong valve 124, the combination and the springs inside of operator '23 are made ready for automatic operation again by manual re-setting, e. g. as described above for the MR-l-Z manual reset valve.

Due .to gas pressure in pipe I located on the delivery side of valve 24, there is flow of gas through the very fine orifice of, jet 3 and to the pilot flameby way of pipe 2 and an ordinary pilot burner located at the upper end of pipe 2. Flow of "gas through jet 3 produces suction or ejector action and-flow of gas from a point near the pilot flame wherethe open end Ioftube 8'is located and from a point near the main burner flame where the open end of tube 9 is located to and through the ignition chamber (5, 6 and 1) and up to the jet. Such flow therefore continuously carries atmosphere from the immediate vicinities of the pilot burner and at least one main burner past the flash-back arrester I6, the electrically heated resistor II and over the bimetallic strip or coil I2 where the latter is ordinarily heated to a temperature of about 200 F. by convection heating due to the flow over the coil I2 of the gases which have been heated by their contact with the hot resistor. When the bimetallic strip is installed, it is located so that the tip of its free end will, at 200 F., be midway between tips I4 and I5 of the spring leaf actuators of the two snap action switches, as shown in Fig. 3.

If no leakage of gas is occurring and the pilot burner and main burner are turned on and burning properly so that gas is being consumed without any losses,the suction pulls a mixture of air and burned gases through tubes 8 and 9 into the ignition chamber where they are heated at the surface of the resistor II to about 600 to 800 C. and then passed over element I2 to give the latter a substantially constant temperature of about 200 F. The exact temperature at element I2 will depend mainly upon the temperature and area of the heating resistor, its distance from element I2, and the rate of flow of gases through the ignition chamber. However, the exact combination of these three factors for a given temperature at element I2 can readily be determined by a simple experiment as described below under the heading, Determining Thermoresponsive Element Temperature.

Assuming that the normal non-leak condition temperature at I2 is 200 F. and that an increase or decrease of F. or more will snap the switches, that the main supply valve is in the on position and that pilots and all other burners are functioning properly and none of the selected spaces are supplying any combustible gas to the ignition chamber, then the series circuit which includes the solenoid is maintained continuously so that there is no movement of main bustible gas or vapor and the temperature of bimetal strip I2 will begin to increase. If the different parts of the apparatus have been properly located and selected as described above, then the free end of strip I2 will begin to move toward one or the other of the tips I4 and I5 but will not snap the corresponding switch until an increase of at least 15 F. above 200 F. (i. e. 215 F.) has taken place at strip I2. Such an increase of 15 F. can, as already explained, be made to occur when the proportion of combustible gas or vapor relative to air or like oxidizing gas has reached a value a safe distance below the minimum explosive limit for that particular combination of gases. At 215 F. one of the two switches, 3| and 32, is snapped and the solenoid circuit broken so that the valve operator immediately and automatically closes main supply valve 24. Thus, the main supply of combustible gas is shut off before a truly explosive mixture has time to develop. If, on the other hand, a sudden supply of anexplosive mixture is drawn into the ignition chamber, the mixture will burn and function in the same way to shut off the main supply and there will beno danger of an explosion because of the presence of flash-back arrester I6 which prevents the combustion spreading from the ignition chamber back into the selected space containing the mixture.

After the valve operator 23 causes valve 24 to automatically shut off the main gas supply, the jet 3 ceases to operate and there is no suction or flow of gases through the ignition chamber. For this reason, there is little conduction of heat from -heating resistor I I to strip I2 and the later drops 1 the cold" side. Hence, when the leak is repaired or no more mixtures of combustible gas or vapor with oxidizing gas are present and one is ready to put the apparatus into operation again, it is necessary to first turn front screw 2| and its corresponding back screw on box I0 so as to depress reset pins 31 and 38 and then manually reset operator 23 so that valve 24 is again brought to the on position. As soon as gas begins to flow through jet 3, the suction is again set up in ignition chamber 5, '6 and I and strip I2 is again quickly heated to its normal temperature of 200 F. and assumes a position with its free end midway between switch actuator tips I4 and I5. At this point the screws are backed off of reset pins 31 and 38 and the cycle is completed and the apparatus again in normal operation.

The above cycle relates to conditions where mixtures of combustible gases with gases supporting their combustion are present. In those cases where the current supplying heat to resistor II fluctuates greatly or fails completely the same cycle of operations occurs, but in every case where a temperature decrease takes place first, the switch on the cold side is the only one to be snapped. Nevertheless, for convenience and for safetys sake, both reset pins 31 and 38 are depressed and then released when putting the apparatus back into operation. If the current at terminals I1 and I8 gets too low or fails entirely, the solenoid and valve operator come into play and close the valve before the snap action switch has time to break the circuit. Yet when the main supply valve is thus shut off primarily by failure of the solenoid current, the resultant cooling effect at I2 causes the switch on the "cold side to soon snap and break the circuit. thereby making it necessary to go through the same cycle of operations as already described in order to put the apparatus back into operation.

If jet 3 becomes stopped up or there is a dangerous drop in pressure in the system supplying the combustible gas, the suction through the ignition tube or chamber is greatly weakened or destroyed and this causes a cooling effect at strip I2 which results, as in other similar instances already described, in the main supply being shut off at valve 24. This constitutes another important safety factor present when using the apparatus of Fig. 2.

From the description herein of the method and apparatus of the invention it will be apparent that the invention is of great importance because it is thereby possible to automatically and quickly shut off the main gas supply when 9 any; of .a large number of unsafe circumstances arise; not onlyoutside of the-apparatus but-also within :the apparatuslitself.

Determining thcrmoresponsive element temperature Withreference toFigs. 2, 3 and 4, the switch box: in is unscrewed and removed a short distance away frOmwT-connection 1 without depressing the switch actuators and breaking the solenoid circuit. To insure maintenance of the solenoid Cil'Cllitifiil; is advisable to: screw front screw '2l and its corresponding back screw-into switch box l0. beforeremoving the latter from T-connection I in' order that reset; pins 3'l and 38 are kept depressed. After the switch-boxis removed, it is replaced by a rubber stopper carrying. a thermometerin such position that-when the stopperis fitted snugly and in airtight'manner into the .top of T-connection1 the bulb of the mercury thermometer is located alongside :of element. 12; Therubber stopper must fit. tightly murder to maintain 'the suction inthe ignition chamber.

The temperature at strip :l2- is firstirea'd ofi of .thethermometer while ordinary air isabeing delivered to the. ignition chamber and passed over filament II- heated-to about 600 or 700 C. The ordinary air is thenreplaced by ;a known mixture of the gas from the main supply and air which contains a proportion of combustible gas somewhat 2 below the 1 minimum known. to ;constitute'za so-called explosive -mixture. The exact proportion of gas is chosen so as to -provide a factor ofsa'fety. Thati-isto say, a mixture is used: which i contains thelowest proportion of combustible gas at which one desires the apparatus to function so as to shut off the main supply of gas when such mixture is drawn into the ignition chamber during normal operation. While such known test mixture is being drawn over heating .resistor l l,.an.extra amount of heat is generated b'ycombustionof'the'mixture and when the resulting heated gases pass the there mometer 'bulbthey will register a temperature at strip 1 2 higher than thatawh'en ordihlaryfair is passing through the ignitioniichamberf. Such increase in temperature should. be notedrand also the increase intemperature-when tlfe'aoptimum. proportion of -the.combustible gaSiWlth'- air for complete combustion. of theimixture t-isiused in place of the known test mixture first mentioned above.

Knowing the normal operating temperature for strip 12, the temperature when mixtures of the gas with air in proportions safely below the minimum explosive limit are present, and the temperature of strip 12 when proportions are used most favorable to explosion and complete combustion, one is able to choose an element [2 of the necessary construction and strength and locate it so as to keep its free end midway between the switch actuator points l4 and [5 when the apparatus is in operation and there are no gas leaks, yet which will immediately shut off the main gas supply when any proportion of gas with air, at or above the safe limit mentioned above chosen so as to be less than the minimum explosive limit, are drawn into and through the ignition chamber.

For example, electrical heating resistor H can be an 8 inch length of Brown and Sharpe 29- gauge Chromel-A wire wound to give 22 turns, each turn being inch in diameter, and with an overall coil length of inch bent into the form..of.= a single-loop .insideof, but not quite touching, the. walls of. a one-half inchrinside diameter ignition chamber and lying in a plane which isperpendicular to the gas .flow and.lo"- cated about. 1%; .inches from element I2. If tubes. 8 and}! are-bringing in air only and have inside. diameters .of about 4, inch, pipe I an insidediameter of inch, and pipe 2 an-inside diameter of 4 inch, jet 3 being an ordinary jet producinga suction in' the ignition chamber of about 0.2 inch .of water and with city artificial illuminating and heating gas-being supplied at about. 4 to.8 ounces pressure at the main supply valve. 24, then such an arrangement of filament andbimetallicelement will give elementlz a temperature somewhere near to 200.F.. In any instance, element l2 can be selected and located in'the ignition tube sothat. its free end will snap thetwo switches open over a wide range of increases and decreases in temperature. Thus, if the temperature of element l2 under normal non-dangerous conditions is 200 F., the olements. construction and the distance of its free end from the actuator tips, l4 and I5 can be chosen so that a decrease or increase of temperature at element l2 anywhere within the rangej'of 5 F. to 25 F. on either side .of'200 F. (preferably about 15F. on either side) will cause'the main supply-valve to. be shut off. The normal steady non-dangerous condition temperature at element [2 can also be made to vary over .a wide range but-ordinarily willlie within a minimum of .about F. and a maximum of about 25fi Iniflthedetailed description of the invention given above, frequent reference is made to combustible. gases. and, their oxidation or combustion .by. gases. supporting their.v combustion. Wheneverzthe. term. combustible gases and like terms-areused-in the specification and theappendedclaims, we wish the same to be understood as including combustible vapors, such as gas like vapors of gasoline, alcohols, ethersand other volatile organic combustible compounds and materials, -inaddition to those substances which are normally gaseous at ordinary temperatures.

Although the new apparatus for putting into operation warningand gas flow regulating means is illustrated largely by reference to gas flow shutoff means, .it.is to be understood that this is only one variation. of the invention which, in its broader sense, embodies the putting into opera tion of a source of power in response to predetermined temperature changes at a temperature responsive stage of the method, whether the source of power is used to operate known warning devices such as bells, whistles, visual signals, etc., or to operate known gas flow shut-off mechanisms such as valves, pinch cocks and clamps, etc., or both.

From the above description, it will be evident to those skilled in the art that numerous variations of the apparatus for gas flow control and/or warning are possible within the broad scope of the invention. An important combination is that whereby a source of power is released at a thermoresponsive stage, whether the power is to be utilized for warning purposes or for merely regulating or shutting off gas flow. Thus, the invention includes broadly an apparatus for gas flow regulation or warning which operates to pass a current of gas which may contain a combustible mixture of gases through a flash-back arresting zone, capable of removing heat from an ignited mixture of gases with sufiicient rapidity to quench combustion of the same, into and through an enclosed ignition zone containing a normally functioning source of heat which first normally brings said current to a temperature at least great enough to burn any combustible mixture contained therein and then, by virtue of the flow of said current of gas, normally maintains the temperature at a selected thermoresponsive point located in the path of the flow beyond the heat source at a substantially constant value, but said temperature at said point fluctuating away from its normal constant value by at least predetermined safe minimum increases and decreases of temperature caused respectively by presence of combustible mixtures in the original current and by failure of the normally functioning source of heat to keep the temperature at the selected thermoresponsive point at its normal constant value, causing heat energy changes corresponding to said fluctuations of temperature to operate temperature responsive power releasing means located at said point and utilizing the power released to operate gas flow control and/or Warning means.

As above described the apparatus is essentially a means for detecting danger or possible danger in connection with a gas distributing system, which detecting means may be utilized either for operating an alarm or for cutting off the gas supply thereby automatically preventing danger. The dangers which can be detected are, first, the presence of an inflammable mixture of gas and air in some selected space such, for instance, as a room in which a gas burner is located; second, a drop in pressure of gas in the supply line which might result in the extinguishing of a gas burner with subsequent leakage of gas therefrom; third, any inoperativeness of the detecting means is detected. Thus aside from whether the apparatus is used as an alarm or for cutting ofl the gas supply, it will always indicate danger or possible danger.

What we claim is:

1. Means for detecting danger of the presence within a selected space of an inflammable mixture of air and gas escaping from a supply; comprising a nozzle connected with the combustible gas supply and normally emitting a continuously flowing jet of gas therefrom, an ejector operated by the velocity of said jet, a conduit connected to said ejector through which a sample stream of atmosphere is withdrawn by said ejector from said selected space, a flashback arresting means in said conduit, heating means beyonrl said flashback arresting means for igniting said stream whenever ignitable or raising its temperature if nonignitable, a thermo responsive element located in heat transferring relation to a portion of said stream beyond said heating means, and a danger detecting element operated by a predetermined response of said thermo responsive element.

2. The construction as in claim 1 in which the thermo responsive element is normally held in neutral position, and is operated to actuate said danger detecting element alternatively by an increase or decrease of temperature transmitted thereto.

3. The construction as in claim 2 in which the danger detecting element is actuated by a predetermined decrease of pressure of the gas at. the source.

4. The construction as in claim 2 in which the danger detecting element is actuated by a predetermined drop in temperature of the heating and igniting means.

5. The construction as in claim 3 provided with a normally open shutoff valve for the gas supply, and means operated by the actuation of said danger detecting element for closing said shutofi valve.

6. The construction as in claim 3 provided with an alarm, and means operated by the actuation of the danger detecting element for operating said alarm.

GEORGE L. WEISSMAN. HOWARD A. GRAFFIS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,644,123 Griswold Oct. 4, 1927 1,681,698 Brooks Aug. 21, 1928 2,062,605 Peters Dec. 1, 1936 2,149,441 Jacobson Mar. 7, 1939 2,219,391 Jacobson Oct. 29, 1940 2,355,090 Love et al Aug. 8. 1944 2,373,326 Miller Apr. 10, 1945 

